Historically, the usual means for propelling objects along the ground has been by employing wheels. Typically at least one wheel is made to move by means of a motor. The wheel so driven exerts force on the ground as it turns, and the object to which the wheel is attached will move forward. A common example of such a method is that of propulsion of automobiles. Another means for propelling or moving objects is a propeller. A propeller will push against a fluid in which an object is immersed and thereby propel the object forward. Simple examples would be the motion of an airplane propeller against the fluid air or the motion of a boat propeller against the fluid water. A different means of propulsion is inertial reaction in which mass is expelled in one direction, causing an object expelling the mass to move in the opposite direction, by virtue of conservation of linear momentum. A simple example of such motion would be the motion of a rocket or a jet airplane.
Although there are numerous examples of the use of wheels, propellers, and reaction engines to impart translation motion, there appear to be relatively few examples of the use of vibrations to induce motion. Of the few vibratory examples, most involve the use of vibrations imparted to the entire surface on which the moving object is travelling. One such example is the use of vibratory conveyor belts to move grain or small parts in manufacturing operations. There is also a toy sports game in which miniature football players are moved along a playing field, which is a sheet of metal, by vibrations to the entire playing field induced by an electromechanical motor (such as a buzzer). However, there are no devices wherein there is a self-contained and mobile source of vibrations that cause an object to move translationally in a directable manner.